Apparatus for checking numbering during printing of paper currency



April 16, 1968 G. GIORI 3,377,948

APPARATUS FOR CHECKING NUMBERING DURING PRINTING OF PAPER CURRENCY Filed Dec. 15, 1966 3 Sheets-Sheet 1 April 16, 1968 (5, 5105 3,377,948

APPARATUS FOR CHECKING NUMBERINO DURING PRINTING OF PAPER CURRENCY Filed Dec. 13, 1966 5 She ts-Sheet April 16, 1968 G. GIORI APPARATUS FOR CHECKING NUMBERING DURING PRINTING OF PAPER CURRENCY 5 Sheets-Sheet :5

Filed Dec. 13, 1966 PIC-3.4

United States Patent 12 Claims. 61. 101--76) ABSTRACT OF THE DISCLOSURE Apparatus for checking numbering of paper currency during printing in which there is provided a numbering mechanism the numbering wheels of which are driven stepwise after each impression of a number, the advance of the numbering wheels of each numbering unit being detected during each cycle of impression, the correct positioning of the numbering wheels of each numbering unit being detected after the advance of the numbering wheels before the following impression phase by means of a detecting system together with means for stopping the printing process after detection of an error before the following paper to be printed receives an incorrect number or one which is printed in the wrong place. To each numbering wheel of the numbering unit are assigned detectors capable of distinguishing between a correct position before impression and an intermediate position of the numbering wheel corresponding thereto and which delivers an actual signal during an advance of the numbering wheel, and an electronic numbering storage system operated at each turn of the cylinder of the numbering device after a phase of impression and before the advance of the first numbering unit and at the beginning of the next impression phase, there being a comparing unit in which real signals of the detector are first compared with an ideal signal representing a number stored in the store of numbers and in which the state of the detectors corresponding to a correct position of the numbering wheels in the new position of impression are then checked as well as a relay controlled by the comparing unit in the case of the detection of a flaw in order to interrupt the printing process.

This invention has for its object a process and an apparatus for checking the numbering during the printing of paper currency by means of numbering devices the rolls of which are moved by one number after each impression.

Paper currency, in particular bank notes, lottery tickets and cheques must be consecutively numbered for reasons of security and checking. This continuous numbering is placed on the finished paper currency by means of a numbering device through which pass the finished bills.

The checking of the numbering as well as of the correct positioning of each of the numbers of a printed number is etfected exclusively by inspection of the finished paper currency. This visual control work requires a considerable time and requires an inordinate care and attention on the part of the checker. This checking is furthermore rendered difiicult by the fact that the number given to the paper currency generally appears in several places and often vertically as well as horizontally. The paper currencies incorrectly numbered must be eliminated and replaced by others bearing a correct numbering. For security reasons, this necessary measure is undesirable as the goal sought is the automation of the manufacture up to the packing so that manual operations in the manufacturing process should be avoided and even rendered impossible.

"ice

In order to facilitate the checking of the numbering, it has been proposed to use a special ink for printing numbers and in particular magnetic ink and to control the numbering automatically by means of detectors responsive to the ink used. In this fashion, it is certainly possible to avoid visual control but it remains necessary to remove the defective paper currency and to replace it by others.

The invention has for its object to bring a completely new solution to this problem of the checking of the numbering of paper currencies in such a way that printing flaws be totally eliminated, while avoiding a replacement of the finished paper currencies which is very important owing to security reasons. To this effect, the process according to the invention is characterised in that during each printing cycle, there is detected, in a first phase of detecting the advance of the printing wheels of each numbering device and in a second phase the correct position of the printing wheels of each numbering device after the advance of the device and before the printing phase following, and this by means of a detecting system and that during the noticing of an error, the printing process is interrupted before the following paper currency receives a wrong number or a number incorrectly placed.

The invention also has for its object a device for carrying but the process. This device is characterised mainly by the fact that it comprises detectors associated with to each printing wheel of a numbering device and capable of distinguishing between the correct position of the wheel and an intermediate position and giving off real signal, an electronic circuit for storing numbers switched over at each turn of the cylinder of the numbering after a printing phase and before the advance of the numbering device at the beginning of a following phase, a comparison circuit by means of which the real signals of the detector are compared with an ideal signal representing the number registered in the storing device and in which the state of the detectors corresponding to the correct positioning of the printing wheel in the new printing position is detected and has as a relay controlled by the comparison unit in the case of the appearance of a flaw for interrupting the printing process.

Since the conventional numbering devices operate with blocking levers elatsically loaded and engaging in teeth rigid with the printing wheels in order to define a correct position of the printing andas these levers are slightly raised during the advance of the printing wheels by slidingon the flank of a tool, these levers are members which can be detected. Their position in efre'ct is a criteria defining their correct position on the printing wheel indicating that the latter is located in an intermediated position.

According to another characteristic of the invention, the detectors used are formed by miniature switches operated by the blocking levers of each of the printing wheels in such a way that one switch be closed when the corresponding lever occupies a correct position.

It suflices then to detect the position of all the blocking levers during the interval of advance of the numbering devices as well as the position of these levers once the advance has been effected.

Other characteritsics and advantages of the present invention will appear during the description of one embodiment thereof made with reference to the annexed drawing in which:

FIGURE 1 shows schematically a device comprising two numbering cylinders operating with a common impresson cylinder, the impression cylinder being mounted in such a way that it can be momentarily spaced apart from the numbering cylinders;

FIGURE 2 shows an enlarged partial view in crosssection of two numbering cylinders mounted on a common axis and each having a numbering means;

FIGURE 3 is a schematic view of the assembly;

FIGURE 4 shows a diagram illustrating the working phases and the detection during a complete rotation of the numbering cylinder; and

FIGURE shows a similar diagram illustrating another type of detection.

The two numbering cylinders 2 and 3 shown in FIG- URE l are mounted on shafts 4 and 5 cooperating with a common impression cylinder 6 mounted on shaft 7. The sheet to be numbered 1 passes through the numbering device in the direction indicated by the arrow. The direction of rotation of each of the cylinders is also shown by corresponding arrows.

Shaft 7 of the impression cylinders turn in a mobile support 8 linked to piston 9 of a hydraulic cylinder 10, controlled by an electro-hydraulic relay 13 through conduits 11 and 12. When a flaw has been detected, piston 9 and hence cylinder 6 are abruptly driven toward the right in such a way that cylinder 6 no longer contacts numbering cylinders 2 and 3; at the same moment the driving of all these cylinders is interrupted; owing to its inertia, cylinder 6 continues its rotation by a certain angle taking along sheet 1 which however will not receive any impression.

Generally a considerable number of number devices is present in a numbering system, since the uncut sheets comprise a certain number of rows and columns of paper currency printed thereon and passing through the numbering system for the simultaneous impression of paper currency of one sheet, and furthermore each paper currency generally receives the same number several times. According to FIGURE 1, there are disposed for example on each cylinder 2 and 3, 4 numbering means 20 shifted axially (FIGURE 2 All the number means of a cylinder are however disposed inside the arc of a circle which does not exceed generally 180", in order that a predetermined time interval remain between the printing of the last numbering device taken in the direction of rotation (end of a printing or impression cycle) and the printing of the first numbering means (beginning of the followig impression cycle). The numbering systems of large dimensions can contain up to 80 numbering means.

FIGURE 2 shows shaft 4 on which are secured two numbering cylinders 2 and 2' each bearing a numbering mechanism 20, 20' respectively hereafter simply called numbering stamps. While the numbers of numbering stamp 20 are oriented parallel to the axis, those of numbering stamp 20' are oriented perpendicular thereto in such a way that it is possible to print numbers in positions-and orientations which differ as is generally the case. The numbering stamps comprise an advance lever 21, 21 respectively cooperating during the rotation of the cylinder with cams 19 and 19' rigid with the machine in such a way that during this rotation of the cylinder, the lever receives one impulsion during the advance of the numbering stamp. These cams 19 and 19 are formed preferably by segments which are bent back and have a variable radius with respect to shaft 4 and on which slide or roll levers 21 and 21'.

As shown on FIGURE 2 a detecting unit 22, 22' respectively is assigned to each numbering stamp 20, 20' in order to watch the position of the printing wheels of each numbering stamp. One such detecting unit 22 is shown on FIGURE 3 in combination with the schematic view of a control device.

Numbering stamp 20 shown on FIGURE 3 comprises 6 numbering wheels A to F thus permitting to print 6 digit numbers. The teeth of each of the Wheels are represented by reference character 23A to 23F. With each of these teeth cooperate a blocking lever 24A to 24F in such a way that it engages by its free end between two teeth when the printing wheel occupies a correct position ready to print, the numbers being perfectly aligned in this position. In all intermediate positions of one or the other of the wheels, lever 24 corresponding thereto is deviated from its normal position.

The advance of the numbering stamp takes place, as mentioned above, by the movement of the advance lever 21 in the direction of arrow F under the action of cam 19; lever 21 then goes back to its rest position (arrow F The detecting unit 22 comprises a number of miniature switches the actuating buttons of which 25A to 25F are located facing levers 24A to 24F and in contact therewith buttons 25 bear mobile electric contacts 26A to 26F urged into closed position by springs 27A to 27F. For as long as a lever 24 is in its rest position, the miniature switches are closed, that is to say that the mobile contact 26 is urged by spring 27 against the contact connetce-d to the end of a line 28A to 28F. If on the contrary, a numbering wheel occupies an intermediate position, the blocking lever corresponding there to 24 pushes back contact 26 against the urging of spring 27. The movement of opening the contact is indicated by arrow F By means of modern miniature switches, it is possible to obtain an opening of the switch by means of a movement of the lever of only 50 microns. Furthermore, the elongations necessary for the opening of the switches allows adjustment within very narrow limits and thus permit an adaptation of the space to different types of numbering stamps.

Additionally, the wear of modern miniature switches is minimal in such a way that it is possible to obtain a number of switching actions of the order of 10 without upkeep or replacement thereof.

Furthermore the detecting circuit is designed in such a way, as described further, that the printing process is stopped in the case where a switch closes or opens at the wrong time.

The control circuit comprises an electronic store 31 associated with numbering stamp 20 at the rhythm of the advance of the numbering stamps at each turn of the numbering cylinder, and the last number shown of which corresponds to the ideal value which the numbering stamp must show as a real or actual value after its stepwise advance. This advance of store 31 occurs during the interval between the printing phase of numbering stamp 20 (interval T FIGURE 4) and the advance of numbering stamp 29 at the beginning of the following printing cycle (interval T FIGURE 4). This moment of advance of the circuit of electronic store 31 is designated by T in FIGURE 4. This advance upon each turn of the numbering cylinder is ensured by an impulse generator not shown controlled by the rotation of shaft 4 of the numbering stamp and which is energised during each passage of shaft 4 to a certain angular position and which delivers then an advance impulse to store 31 through line- Outlets 28A and 28F of the miniature switches, associated with each of the number wheels A to F are linked to a comparison unit 30 to which are also applied the outlets 33A to 33F of the storing circuit 31. These outlets 33A to 33F are ascribed to each of the ciphers of the number stored corresponding to the number of the numbering stamp that is to say line 33A to the units, and line 33B to the tenths etc. In the example under consideration, the number momentarily recorded for checking of numbering stamp 20 which corresponds to the correct position of numbering wheels A to F of numbering stamp 20, represented by the state of reference stores by 36 in the comparison unit 30, each store 36 being assigned to a decimal of the stored number. It has proven particularly advantageous to use magnetic memory systems, the state of magnetisation of demagnetisation represents the number stored.

In similar manner, the positioning of numbering wheels A to F of numbering stamp 29 are shown by reference stores 35 which consist of magnetic core memories in comparison unit 30, the state of these memories of store 35 ascribed to the numbering wheels being modified by the opening of one or several miniature switches in position or in a new position. Beginning with the last positioning of the numbering stamp during the preceding impression phase, there is noticed that in every case the miniature switch 25A ascribed to the wheel of units A remains open for a certain time in the advance of the numbering stamp to point T (FIGURE 4), which has for effect to occasion a change in the magnetic state of the corresponding memory of store 35 if the opening time of miniature switch 25A extends beyond a certain interval. This necessary interval is the minimum time necessary for the change of the magnetic state of the corresponding memory of store 35 and is selected in such a way that bearing in mind the statistical variations in the possible tolerances of the mobile mechanical parts, this value is on the level with or below the lower limit of the interval necessary for a numbering wheel of the numbering stamp to advance positively by one step.

The duration of the movement during the advance corresponds, as described above to the raising of the corresponding lever 24 and by that to the duration of the opening of the corresponding minature switch. Immediately after the advance of the numbering stamp 20, the states of the store system 36 and of the store system 35 subordinated to the number wheels are compared in unit 30. Since the advance of the system of reference 36 has already been effected by the number store at time T the stored values of the reference stores 36 and of the store system 35 must correspond exactly at time T (FIG- URE 4). Particularly, only the store systems ascribed to the units of the numbers of the two reference stores 35 and 36 can change during the advance inside the same decade, while all the stored elements assigned to the other decimals of the number must remain unchanged. During the passage to the following decade, the stored elements assigned to the tenths and to the units can however be modified if the advance of the numbering stamp is correct. In a similar manner there occurs a change in the hundreds, the thousands. If a comparison of the state of the stores 35 and 36 taking place at time T denotes a difference, an alarm signal is then transmitted to switch 13 by unit 30 through outlet line 34. Switch 13 then actuates system 9 and interrupts the pressure as described with respect to FIGURE 1.

It is naturally not necessary that the effective number of the numbering stamp be reproduced in a binary code by the reference stores 35 and 36, but it suifices in principle that the magnetic state of the stored elements of s stem 35 and 36 be modified in alternate fashion during the arrival of a number of advance coming either from the memory 31 or from the miniature switch 25 (if the opening time of this switch reaches the minimal time interval). It is not possible that the reference stores 35, 35, respectively, assigned to the units be openly magnetised and demagnetised, respectively magnetised inversely, while the stored elements 35 and 36 assigned to the tenths, hundredths, undergo a change of state during the arrival of the order of advance on the lines of the tenths, the hundredths, etc. The movements of lever 24 of the numbering stamp during a minimum interval predetermined eflectively a certain criteria that the numbering wheel corresponding has advanced. If following a mechanical failure of the numbering stamp one of the numbering wheels to be moved has moved too rapidly under the action of advance lever 21, in such a way that the wheel has advanced by two steps or even more, blocking lever 24 falls after remaining up for an abnormally short time for a brief lapse of time in the following interval into corresponding teeth 23, which occasions the premature closing of the miniature switch corresponding thereto and its reopening. The operation of the switch occasions a change in the magnetic state of reference store 35, which has for result to signal a flaw.

Furthermore it is naturally possible to provide a reference element 36 and a storage element assigned to the numbering stamp in such a way that the numbers to be compared are represented clearly which is possible in the storage systems and in the binary counters generally used.

By the detection phase described taking place at instant T which is dynamic surveillance, since there is controlled then in this phase the advance of the numbering stamp, it is not however yet possible to control the correct rest position of all the blocking levers 24 after an advance, that is to say, the correct alignment of all the ciphers of the following number ready to be printed. The possibility exists in effect that the numbering Wheel be driven but does not come to occupy its correct position because of an excess friction or of dirt, which has for effect to move one cipher with respect to the others or to only print it partially. It is therefore necessary to introduce between intervals T of the advance numbering stamp and the following printing phase T :1 static detecting phase, T after instant T after instant T unit 30 verifies the closing of all switches 25. This condition fulfilled indicates that all the blocking levers occupy their correct rest position corresponding to a correct alignment of the ciphers of the numbering stamp. If during this static detecting phase T unit 30 notices that a switch is open, it will send an alarm signal on line 34 to switch 13 which actuates piston 9 separating cylinder 6 from cylinders 2 and 3 (FIGURE 1). In this way it is thus possible to eliminate the printing flaws due to an incorrect alignment of ciphers which can be then partially printed.

It is thus practically impossible that a flaw pass unnoticed during one or the other of the two phases of detection. All operating flaws of the numbering stamp, including a rupture of a blocking lever or of a switch or even a failure on the part of the storage circuit 31 or of 35 and 36, will trigger the alarm signal.

As mentioned above each numbering unit comprises generally several numbering stamps shifted one with respect to the other along the circumference of the circle of the cylinder, as well as several numbers cylinders each bearing a certain number of numbering stamps. In this case, a comparison unit 39 is assigned to each numbering stamp with reference stores 35 and 36 corresponding theerto, the entire storage system of reference stores 36 being controlled by a common number storage 31 associated to a complete numbering unit. This centralised control naturally takes place during an interval of time between the impression of the number last printed during a printing cycle and the advance of the numbering stamp first printing during the following cycle. On FIGURE 3 there has been shown a system corresponding to the outlet lines 33, 33" of the storage of central numbers 31; these systems lead to comparison units 30 corresponding thereto and assigned individually to the numbering stamps. Before the placement in service of the numbering unit, it sufiices to check all the stores of reference 36 are in correct initial state correspondin to the initial numbers, generally different for each numbering stamp. The numbering stamp being shifted circularly, their advance will take place at different moments indicated on FIG- URE 4 by T T etc. Consequently, the dynamic detection takes place at moments T T etc. The static detection can naturally be effected individually at different instants T eventually which has not been shown on FIGURE 4. The only condition determining the choice of time T is constituted by the fact that between the time T and the following impression T it is necessary that a sufficient interval be provided in such a way that in case of an error is detected a printing flaw be avoided.

On FIGURE 4 there is shown schematically the functioning diagram of the detection device as a function of the angular position of the shaft of the printing cylinders. The reference po iian 0 has been selected arbitrarily immediately before the printiig phase T After about a quarter of a turn, there occurs at moment T the advance of the number store 31 and therewith that of the storage system of reference 36 of all the comparison units 30. At moments T T T the individual numbering stamps move by a unit and the reference store 35 subordinated to these numbering stamps also advance by a unit. Immediately after this advance there occurs at the instants T T T the dynamic detection described during which the state of the reference storage systems and the state of the storage systems subordinated to the numbering stamps are compared mutually. At instant T there is determined finally if all the blocking levers of the numbering stamp occupy their correct rest position that is if all the switches are closed. If during one or the other of the detection phases, an error is detected, switch 13 is energised by an alarm signal and stops the printing.

The switches 25 can be connected in such a way that they be open when the blocking lever occupy their rest position and closed during the raising of the lever, that is, during the advance of the numbering wheels.

FIGURE 5 shows also a functioning diagram of a detection device in which the surveillance effected duriig the first phase of detection designated by T; on FIG- URE 4 takes place by means of a different circuit. In this case, the comparison unit works with coincident circuits in such a way that during the first phase of surveillance there is controlled directly the duralion of interval t3, during which the blocking lever of a numbering wheel is shifted from its rest osition during the advance of this Wheel. Instead of using a signal changing a storage element at time T there is sent a signal of duration 13 to the comparison unit of a duration corresponding to the time in which the switch occupies a position corresponding to the movement phase of a blocking lever. This signal is compared with reference signal :4 emitted by a number store at moment T at the beginning of an advance movement of the numbering wheel corresponding of the numbering stamp. The duration of reference signal t4 is selected in such a way that it corresponds to the duration during which a blocking lever is raised during the correct advance of the numbering stamp by one step taking into consideration the normal functioning speed of the numbering stamp.

The two signals t3 and t4 then coincide within the limits of admissible time toerances. If this coincidence is not realised, that is if signal :3 of the switch is shorter or longer than the reference signal inside the prescribed limits, an alarm signal is triggered shutting off the printing process.

Since in this case, the reference signal emitted by the number store is triggered exactly at instant T at which time the advance movement of the numbering stamp begins, there is provided a control of the number stores as a function of the angular posiion of the individual numbering stamps on the cylinder and on the numbering mechanism. Each time that a numbering stamp passes by the angular position at which its advance lever 21 begins to move, an order is given to the number store. The sending of this order can be effected by the advance lever of the corresponding numbering stamp. Reference signals are only sent on outlets 33A to 33F of the number store if the corresponding decimal to one of the outlets has been modified, the advance taking place directly by the order of triggering of the reference signal or before.

The second surveillance phase T during which the correct rest position of all the blocking levers of a numbering stamp is controlled correspond exactly to the detection phase described in relation to the first embodiment.

In this case, the duration of each reference signal t4 can be given equally as a function of the race of the advance lever 21. The reference signal is then generated during the entire duration of the course of lever 21 in such a Way that the detection detection consists in a comparison of the duration of movement of the advance lever of the corresponding duration of rotation of the numbering wheel, or respectively of the numbering wheels. A flaw signal is naturally also sent when for example owing to the braking of an advance lever, no signal t4 or I3 is emitted.

The invention is not limited to the example described but includes also other types of detectors operating on a magnetical optical base.

The invention can also be used in installations compris ing numbering stamps working with cylinders driven into rotation, one control group being assigned to each numbering cylinder and provided with a certain number of numbering mechanisms or in presses using planks. Furthermore the state of the storage circuit 31 can be compared with that of detectors 25 by any other electronic means in particular by logical circuits.

What is claimed is:

1. Device for checking machines which print numbers on sheets bearing currency and the like, the said machines having at least one rotating numbering cylinder in contact with an impression cylinder and carrying at least one numbering unit having a number of driven spaced numbering wheels equal in number to the highest number of digits to be printed and rotating by an angle equal to one digit after each impression, said device comprising:

(a) position detecting means actuated by each of said Wheels for detecting correct stepwise movement there of before each printing of a number, said means producing a signal characteristic of the number appearing after said stepwise movement, said detecting means being connected in a circuit;

(b) a memory store in said circuit stepwisely actuated upon rotation of said cylinder after each impression of one number and emitting a signal characteristic of the number which should next be printed;

(c) a comparison unit having two groups of inputs, one of said groups being connected to the output of said position detecting means and the other group of input to the output of said memory store, said comparison unit comparing said signals emitted by said detecting means and said store and emitting an error signal when said signals do not correspond;

(d) a relay connected to the output of said comparison unit;

(e) means actuated by said relay for preventing said cylinder from printing upon emission by said comparing unit of an error signal thereby preventing printing of a wrong number.

2. Device for checking numbering machines which print numbers on sheets bearing currency and the like, the said machines having rotating cylinders carrying at least one numbering unit each unit having a number of spaced, driven numbering wheels equal in number to the number of digits to be printed and rotating by a distance equal to one digit after each impression, said device comprising:

(a) position detecting means actuated by each of said wheels for detecting stepwise movement thereof and for detecting the angular position of wheels which have moved before impression thereby, said means producing a first signal characteristic of the number appearing after the stepwise movement, and a second signal characteristic of the correct angular position of all wheels in their printing position, said means being connected in a circuit;

(b) an electronic memory store in said circuit stepwisely actuated upon rotation of said cylinder after each impression of one number and emitting a second signal characteristic of the number which should next be printed;

(c) a comparison unit connected to said detecting units and said store comparing said first signal emitted by said detecting units and said signal emitted by said stores and emitting an error signal when said signals do not correspond, or when the other mentioned signal does not correspond to the correct angular position of said wheels, said unit having two groups of input, one of said groups being connected to the output of said position detecting means and the other of said groups being connected to the output of said store;

(d) a relay connected to the output of said comparison unit;

(e) a mechanism actuated by said relay for preventing said cylinder from printing upon emission by said comparing unit of one of said error signals thereby preventing printing of a wrong number or of an incorrectly positioned number thereby ensuring that said numbering machines always print the night number in the right place on said currency and the like.

3. Device according to claim 2, wherein said position detecting means comprise micro switches for each wheel, each switch having a movable control cooperating with a blocking lever associated with each wheel and engaging teeth in a ratchet wheel integral with said numbering wheel, said lever being lifted during the stepwise movement from a rest position, said micro switch being either closed or open when said lever is in one or the other of its positions.

. 4. Device according to claim 2, wherein said comparison unit comprises two storage units for each numbering unit, the storage states of one storage unit being controlled by the signals from the position detecting means emitted during the stepwise movement and the state of the other by said electronic memory store.

.-5. Device according to claim 4, wherein said storage units are magnetic stores.

6. Device according to claim 4, wherein a change of storage state of the first mentioned storage representative of the next number which should appear on the wheels, occurs only if the time for lifting of the respective blocking lever is greater than a minimum time equal to or less than the time period necessary for the normal movement of the corersponding wheel by one step.

7. Device for checking machines which print numbers on sheets bearing currency and the like, the said machines having at least one rotating numbering cylinder in contact with an impression cylinder and carrying at least one numbering unit having a number of driven spaced nurnbering wheels equal in number to the highest number of digits to be printed and rotating by an angle equal to one digit after each impression, said device comprising:

(a) position detecting means actuated by each of said wheels for detecting correct stepwise movement thereof before each printing of a number, said means producing a signal characteristic of the number appearing after said stepwise movement, said detecting means being connected in a circuit;

(b) a memory store in said circuit stepwisely actuated upon rotation of said cylinder after each impression of one number and emitting a signal characteristic of the number which should next be printed;

(c) a comparison unit having two groups of inputs, .one of said groups being connected to the output of said position detecting means and the other group of input to the output of said memory store, said comparison unit comparing said signals emitted by said detecting means and said store and emitting an error signal when said signals do not correspond;

(d) a relay connected to the output of said comparison unit;

(e) means actuated by said relay for preventing said cylinder from printing upon emission by said comparing unit of an error signal thereby preventing printing of a wrong number, and wherein said comparison unit comprises coincidence circuits for comparing two time periods, one period being equal to the duration of the output signal from said position detecting means during the movement of the corresponding wheel and the other being equal to the duration of the reference signal from an electronic memory store chosen so that said reference time signal corresponds to the time required for the correct stepwise movement of said wheel under actual operating conditions.

8. Device according to claim 7, wherein said reference signal is a function of the movement of an advancing lever, which produces the stepwise movement of the wheel during each revolution of said cylinder. l

9. Device according to claim 3', wherein said second signal corresponds to the correct state of all micro switches in the rest position of said lever.

10. Device according to claim 4, wherein each of said magnetic stores has only two magnetic states.

11. Device for checking machines which print numbers on sheets bearing currency and the like, the said machines having at least one rotating numbering cylinder in contact with an impression cylinder andcarying at least one numbering unit having a number of driven spaced numbering wheels equal in number to the highest number of digits to be printed and rotating by an angle equal to one digit after each impression, said device comprising:

(a) position detecting means actuated by each of said wheels for detecting correct stepwise movement thereof before each printing of a number, said means producing a signal characteristic of the number appearing after said stepwise movement, said detecting means being connected in a circuit;

tb) a memory store in said circuit stepwisely actuated upon rotation of said cylinder after each impression of one number and emitting a signal characteristic of the number which should next be printed;

(c) a comparison unit having two groups of inputs, one of said groups being connected to the output of said position detecting means and the other group of input to the output of said memory store, said comparison unit comparting said signals emitted by said detecting means and said store and emitting an error signal when said signals do not correspond;

(d) a relay connected to the output of said comparison unit;

(e) means actuated by said relay for preventing said cylinder from printing upon emission by said comparing unit of an error signal thereby preventing printing of a wrong number; said means for pre venting said cylinder from printing consisting in a mechanism which places said impression cylinder out of contact with said numbering cylinder.

12. Device according to claim 11, wherein said means for preventing said cylinder from printing are hydraulic.

References Cited UNITED STATES PATENTS 1,502,128 7/ 1924 Smith 101-77 1,691,889 11/1928 Meisel 10176 1,920,232 8/1901 Allen 10177 2,375,174 5/1945 Roesen 101-76 2,683,409 7/ 1954 Dutro et a1 10*1247 2,912,926 11/ 1959 Haskin 101-76 WILLIAM B. PENN, Primary Examiner. 

